| In recent years,with the development of wireless communication techniques,terrestrial communication networks have made considerable achievements on improving both the communication speed and the quality of service.However,terrestrial networks are usually deployed in densely populated developed areas,which makes the reliable communication cannot be guaranteed in sparsely populated deserts,oceans,or other areas where base stations are not easy to be established due to geographical factors.Satellite communication,with the characteristics of wide coverage,large capacity,long transmission distance,and high reliability,is realized as an effective approach to solve the abovementioned problems.However,due to the masking effect caused by the obstruction of trees,buildings,or other barriers,the line-of-sight transmission between the satellite and the terrestrial user is unstable.Therefore,it is a general strategy to deploy relays on the terrestrial to improve the reliability of the communication.In the existing related works,a half-duplex relaying is commonly adopted in literature,in which the signal receiving and transmitting cannot be performed simultaneously,resulting in an inefficient wireless spectrum.Instead,the full-duplex(FD)relaying,which can enable signal receiving and transmitting at the same time and frequency,is considered as an effective technique to improve the spectral efficiency.In addition,the non-orthogonal multiple access(NOMA)technique has outstanding performance on improving the spectrum utilization and communication capacity as it can provide services for a large number of users at the same frequency.Therefore,this study integrates the NOMA technique into the satellite communications to investigate the system performance of hybrid satellite-terrestrial communication networks under FD relaying mode.The main research contents are as follows:(1)System performance of a hybrid satellite-terrestrial NOMA communication network in the FD relaying mode is investigated.In this system,the satellite transmits a NOMA signal to a FD relay,which decodes and forwards the information to the two users simultaneously.Considering that the satellite channel experiences Shadowed-Rician fading and the terrestrial channels are subject to Nakagami-m fading,both exact and asymptotic expressions of outage probability(OP)for two NOMA users are derived in the presence of residual self-interference(SI)as well as the FD relaying.The correctness of the theoretical expressions is verified by Monte-Carlo simulations.In addition,the influence of shadowing severity levels,power allocation factors,and residual SI channel coefficient on the system outage performance is also analyzed.(2)Analyze the system performance of a hybrid satellite-terrestrial NOMA communication network under multi-antenna scenarios.Based on the system proposed in Content(1),the spatial-diversity technique is applied to counteract the channel fading.Specifically,both the satellite and the user nodes are equipped with multiple antennas.In addition,the satellite adopts a maximum ratio transmission scheme to transmit a NOMA signal to the FD relay,and the FD relay deploys a decode-and-forward protocol to forward the information to two users simultaneously,which employs the maximum ratio combining strategy to process the received signals.Both analytical and asymptotic expressions of OP for two users are presented under the fixed power allocation scheme as well as imperfect successive interference cancellation.Furthermore,the effects of parameters such as the number of antennas and imperfect SIC factors on the outage performance are investigated.Moreover,an adaptive power allocation scheme is considered and the corresponding expressions of the optimal power allocation coefficients are also obtained.In addition,the throughput of the whole system is also analyzed under a delay-limited transmission mode.Finally,Monte-Carlo simulations are adopted to verify the accuracy of the analytical expressions. |
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